Trying to book a room in NUS, needed WebVPN anew, died during installation, vaguely familiar, blog to rescue:

I encountered an error since 27 Feb 2010, apparently there was a server upgrade. I received an extraction error during the installation. Comcen sent me instructions and the critical thing to do was to type this in the Terminal window and respond with the mac’s user password: sudo keytool -storepasswd -new changeit -keystore /System/Library/Frameworks/JavaVM.framework/Resources/Deploy.bundle/Contents/Home/lib/security/cacerts -storepass changeme